The present invention relates to an amorphous optical device. More particularly, the present invention relates to an amorphous optical device having a negative optical input-output characteristic to incident light and advantageously used for optical computers capable of performing ultra-high speed and parallel processing, object recognizing apparatuses in which image optical signals are processed by using image optical signals, motion picture extracting apparatuses used for eyes of robots and object movement monitors and optical surge absorbers for optical communication and optical instrumentation.
Although several methods have heretofore been proposed for preparing a so-called optical inverter, i.e., an optical signal inverter which is indispensable for constructing an optical computer, no devices which can work at low light intensities have been prepared.
A Josephson""s device which is an electronic device utilizing superconduction can work at extreme low temperatures but hardly works at the room temperature. Devices for use at high temperatures using wide gap semiconductors such as SiC are known. However, since the properties of the semiconductors themselves vary with temperature in these devices, it is difficult that the devices are used at extremely low temperatures.
In parallel processing of signals such as image information, a planar optical device is necessary. However, planar devices such as CCD using semiconductor devices cannot perform completely parallel processing since an image must be scanned to process the signal of the image.
Optical devices which have a negative optical input-output characteristic to incident light, perform inversion of optical signals using the negative optical input-output characteristic, and construct optical inverters such as ErYAG crystals obtained by replacing Y (yttrium) in YAG (yttrium aluminum garnet) with Er (erbium), are known. However, growing such crystals requires a long time and, as the result, the obtained crystals are expensive. It is also difficult that a crystal is grown to a large size so that a device having a large area can be obtained.
Optical devices which comprise silica glass fibers doped with Er (erbium) at a core portion, have a negative optical input-output characteristic to incident light, perform inversion of light signals based on the negative optical input-output characteristic, and construct optical inverters are known. However, the number of erbium doped in these silica glass fibers is at most 1xc3x971025 per 1 m3. Silica glass as long as several meters is required to exhibit the negative optical input-output characteristic and a compact device cannot be made.
The modulation degree of modulation light is defined as: Mxe2x89xa1100xc3x97(Imaxxe2x88x92Imin)/(Imax+Imin) (%). In this definition, Imax represents the maximum value of the intensity of the modulation light and Imin represents the minimum value of the intensity of the modulation light. In the case of ErYAG crystals obtained by replacing Y (yttrium) in YAG (yttrium aluminum garnet) with Er (erbium) and the silica glass fibers doped with Er (erbium) at a core portion, the modulation degree (M) of the transmitted light is at most 20%. Therefore, the processing of images and optical signals tends to be affected by noise and improvement has been desired.
The present invention has an object of providing a novel amorphous optical device which contributes to economic construction of optical computers and, by enabling economic parallel processing of signals such as image information, contributes to development of optical computers capable of performing ultra-high speed and parallel processing, object recognizing apparatuses in which image optical signals are processed by using image optical signals, motion picture extracting apparatuses used for eyes of robots and object movement monitors and optical surge absorbers for optical communication and optical instrumentation.
As the result of extensive studies by the present inventors to achieve the above object, it was found that an amorphous material doped with an element having a negative optical input-output characteristic to incident light in a high concentration exhibits an excellent negative optical input-output characteristic to incident light and a large modulation degree (M) of transmitted light in a small thickness. The present invention has been completed based on this knowledge.
The present invention provides:
(1) An amorphous optical device which is doped with an element having a negative optical input-output characteristic to incident light, wherein the number of ions and/or atoms of the element is 1xc3x971026 to 2.8xc3x971028 per 1 m3 of an amorphous material, and has a negative optical input-output characteristic to incident light;
(2) An amorphous optical device described in (1), wherein the element having a negative optical input-output characteristic to incident light is a rare earth element or a transition element;
(3) An amorphous optical device described in (2), wherein the rare earth element is Er (erbium);
(4) An amorphous optical device described in any of (1) to (3), wherein the amorphous material is a glass;
(5) An amorphous optical device described in (4), wherein the glass is a borate glass, a phosphate glass, a silicate glass, a borosilicate glass, an aluminosilicate glass, a tellurite glass, a fluorophosphate glass or a fluoride glass;
(6) An amorphous optical device which comprises amorphous optical device described in any of (1) to (5) shaped two dimensionally and controls image optical signals directly by using image optical signals; and
(7) An amorphous optical device described in any of (1) to (6), which uses light obtained by spectrally splitting or filtering sunlight, thermal radiation light or light emitted from a fluorescent material by electrons emitted by electric field, or laser light as a light source.